1. Prepare grill.
2. Combine first 4 ingredients in a medium saucepan. Cook over low heat until cheese melts, stirring constantly. Set aside 1/2 cup sauce; keep remaining sauce warm.
3. Sprinkle steak with salt and pepper. Place steak on grill rack coated with cooking spray; cover and grill 18 minutes on each side or until desired degree of doneness, basting often with 1/2 cup sauce.
4. Cut steak diagonally across grain into thin slices. Serve with remaining sauce.
carbo rating: 1